Preparation And Photocatalytic Performance Of Modified Bismuth Oxide

Bi2O3 is an important semiconductor material,which is considered to be a new generation of extremely promising catalytic materials due to its low band gap and visible light response.However,the high recombination rate of photogenerated electrons and holes in Bi2O3 limits its practical application in photocatalysis.Hence,the modification of Bi2O3 has become a research hotspot.Doping is a widely used method to change the physical properties and carrier transport of materials.Considering the rich energy level structure and unique properties of rare earth elements,lanthanum and cerium are selected to modify Bi2O3 in this dissertation.By using the particular electronic structure of rare earth elements,the active species on the surface of photocatalyst can be improved,so as to improve the photocatalytic performance.The main contents of this dissertation are as follows:1.Pure Bi₂O₃ and Bi₂O₃ with different La contents photocatalysts were prepared via sol–gel method,and citric acid as an organic complexing agent.XRD results showed that a small amount of La³⁺did not change the crystal form of Bi₂O₃.The band gap width of the material was determined by UV–Vis diffuse reflectance absorption spectra.By the analysis of X–ray photoelectron spectroscopy?XPS?,it was found that La3+doping could create oxygen vacanices?OVs?on the surface of Bi₂O₃,and it was confirmed by electron spin resonance technology?ESR?technology.O2 temperature programming desorption experiment confirmed that the surface of catalytic adsorbed some oxygen.Methyl orange?MO?and phenol were used as target pollutants to study the photocatalytic activity of La–doped Bi₂O₃.The results show that La doping improves the catalytic ability,and 2%La–Bi₂O₃ has the highest photocatalytic activity.The results of Photoluminescence?PL?spectroscopy,transient photocurrent response and electrochemical impedance spectroscopy indicated that La³⁺doping could effectively prevent the recombination of photogenerated electron hole pairs and improve the separation efficiency.The mechanism of synergistic effects of La3+and oxygen vacancy?OVs?to inhibit electron hole recombination and improve photocatalytic activity was proposed.2.Pure Bi₂O₃ and Bi₂O₃ with different Ce contents photocatalysts were synthesized via one–step ethylene glycol–assisted solvothermal method.XRD results showed that a certain amount of Ce doping could change the crystal form of Bi₂O₃,and the high temperature face–centered cubic phase?–Bi2O3 could be obtained.The band gap width and conduction band potential of Bi2O3 had undergone corresponding changes due to the influence of Ce doping.By analyzing the X–ray photoelectron spectroscopy,it was found that Ce existed on the surface of Bi₂O₃ in a mixed valence state of+3 and+4.Phenol was used as pollutant to study the photocatalytic activity of Ce–doped Bi2O3.The 0.8 Ce–Bi2O3 sample with a doping ratio of0.8wt.%presented the highest photocatalytic activity.Photoluminescence?PL?spectroscopy,transient photocurrent response,and electrochemical impedance spectroscopy had shown that the improvement of the visible light catalytic efficiency of 0.8 Ce–Bi2O3 catalyst was mainly due to the effective separation and transmission of photo-generated carriers.The mechanism of Ce3+/Ce4+redox reaction to promote the separation of photogenerated electron holes and increase the photocatalytic activity in visible light was proposed.